Differential assembly with preload adjustment mechanism

ABSTRACT

A vehicle differential assembly may include a differential housing rotatable about an axis, a first output assembly, a pinion gear, and a first coupling assembly. The first output assembly may include a first side gear and a first output member. The first side gear may be disposed within the differential housing and may be rotatable about the axis. The first output member may be coupled to the first side gear for rotation therewith. The first coupling assembly may be engaged with the first output assembly and may include a coupling mechanism and a biasing member. The coupling mechanism may extend through an opening in the first output member and may be displaceable relative to the differential housing in a direction generally parallel to the axis. The biasing member may be engaged with the coupling mechanism and may urge the first output assembly into frictional engagement with the differential housing.

FIELD

The present disclosure relates to differentials for use in automotivedrivelines, and more specifically to limited slip differentials.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Differential assemblies provide for speed differentiation between a pairof driven wheels. Typically, a differential assembly includes adifferential housing rotatably driven about an axis by a ring gear thatis fixed thereto. The differential assembly may include mated pairs ofside gears and pinion gears rotatably supported within the differentialhousing. Output shafts extend within the differential housing. Eachoutput shaft includes an end fixed for rotation with one of the sidegears.

Limited slip differential assemblies operate to provide at least someoutput torque to each output shaft regardless of the coefficient offriction between the driven wheels and the ground. At least one limitedslip differential assembly includes a side gear frictionally engagedwith the differential housing. The frictional engagement may be providedby a spring applying a predetermined engagement force. The predeterminedengagement force is not adjustable.

SUMMARY

A vehicle differential assembly may include a differential housingrotatable about an axis, first and second output assemblies, a piniongear, and a first coupling assembly. The first output assembly mayinclude a first side gear and a first output member. The first side gearmay be disposed within the differential housing and may be rotatableabout the axis. The first output member may be coupled to the first sidegear for rotation therewith. The second output assembly may include asecond side gear and a second output member. The second side gear may bedisposed within the differential housing and may be rotatable about theaxis. The second output member may be coupled to the second side gearfor rotation therewith. The pinion gear may be disposed within thedifferential housing and may be engaged with the first and second sidegears. The first coupling assembly may be engaged with the first outputassembly and may include a coupling mechanism and a biasing member. Thecoupling mechanism may extend through an opening in the first outputmember and may be displaceable relative to the differential housing in adirection generally parallel to the axis. The biasing member may beengaged with the coupling mechanism and may urge the first outputassembly into frictional engagement with the differential housing.

The coupling mechanism may further include an adjustment member to varya load applied by the biasing member.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a schematic illustration of a vehicle according to the presentdisclosure; and

FIG. 2 is a sectional view of the rear axle assembly of FIG. 1.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Whilethe following description is directed to a bevel gear differentialassembly, it is understood that the description applies equally tohelical gear differential assemblies.

With reference to FIG. 1, a vehicle 10 may include an engine 12, atransmission 14, a propeller shaft 16, and a rear axle assembly 18.Transmission 14 may include an output shaft 20 engaged with propellershaft 16. Propeller shaft 16 may be engaged with rear axle assembly 18.Rear axle assembly 18 may include a pinion shaft 22, a differentialcarrier 24, a differential assembly 26, and first and second axle shafts28, 30 drivingly coupled to wheels 31. Pinion shaft 22 may be engagedwith and driven by propeller shaft 16 and may extend into differentialcarrier 24. Pinion shaft 22 may include a pinion gear 32 thereon engagedwith differential assembly 26.

With reference to FIGS. 1 and 2, differential assembly 26 may berotatably supported within differential carrier 24 by bearing assemblies35, 37 and may include a differential housing assembly 34, first andsecond output assemblies 36, 38, a pinion assembly 40, and first andsecond coupling assemblies 44, 46. Differential housing assembly 34 mayinclude a differential housing 48 and a ring gear 50 rotatable about anaxis 51. Ring gear 50 may be fixed to differential housing 48.Differential housing 48 may include a body defining a central cavity 52having a series of thrust washers 54, 56, 58, 60 therein, and first,second, third, and fourth openings 62, 63, 64, 65 extending therethroughand in communication with central cavity 52. Ring gear 50 may bemeshingly engaged with and driven by pinion gear 32.

First output assembly 36 may be generally similar to second outputassembly 38. Therefore, second output assembly 38 will not be describedin detail with the understanding that the description of first outputassembly 36 applies equally to second output assembly 38. First outputassembly 36 may be frictionally engaged with differential housing 48 forrotation about axis 51. First output assembly 36 may include a firstoutput member 66, a first side gear 68, and a first thrust bearing 70.First thrust bearing 70 may be disposed between first output member 66and differential housing 48. First output member 66 may include anoutput shaft 72 having a flanged end 74.

Output shaft 72 may extend into first opening 62 in differential housing48 and may have an end 76 opposite flanged end 74 located within cavity52. End 76 may be splined and may have first side gear 68 in a splinedengagement therewith. As a result of the splined engagement, first sidegear 68 and output shaft 72 may be coupled for rotation with one anotherand first side gear 68 may be axially displaceable relative to outputshaft 72 to provide an adjustable preload engagement between first sidegear 68 and differential housing 48, as discussed below. Output shaft 72may include an aperture 78 extending therethrough for engagement withfirst coupling assembly 44 to provide the adjustable preload engagement.

Pinion assembly 40 may include a pinion shaft 80, and first and secondpinion gears 82, 84. Pinion shaft 80 may be disposed within third andfourth openings 64, 65. First and second pinion gears 82, 84 may besupported for rotation about pinion shaft 80 as well as axialdisplacement relative thereto.

First coupling assembly 44 may be generally similar to second couplingassembly 46. Therefore, second coupling assembly 46 will not bedescribed in detail with the understanding that the description of firstcoupling assembly 44 applies to second coupling assembly 46. Firstcoupling assembly 44 may include a coupling mechanism 86 and a biasingmember 88. Coupling mechanism 86 may include a bolt 90, a washer 91, anda nut 92. Bolt 90 may include a head 94 having a shank 96 extendingtherefrom. Head 94 may extend axially outwardly from a first end ofaperture 78 in output shaft 72 and a second end 98 of bolt 90 generallyopposite head 94 may extend axially inwardly from first opening 62 andinto cavity 52. Washer 91 may be disposed between head 94 and biasingmember 88 and may be engaged with biasing member 88.

Second end 98 of bolt 90 may include a threaded portion 100 forengagement with nut 92. Nut 92 may include a generally cylindrical bodyhaving first and second portions 93, 95 at opposite ends thereof. Firstportion 93 may be in splined engagement with first side gear 68 and mayabut end 76 of output shaft 72. Second portion 95 may form a flangeextending radially outwardly relative to first portion 93. Secondportion 95 of nut 92 may abut first side gear 68 and may generally urgefirst side gear 68 axially outwardly toward thrust washer 54. The forceapplied to first side gear 68 by nut 92 may generally be determined bythe axial location of head 94 and the characteristics of biasing member88.

Biasing member 88 may generally urge coupling mechanism 86, andtherefore first side gear 68, axially outwardly in a direction generallyparallel to axis 51. More specifically, biasing member 88 may bedisposed between head 94 of bolt 90 and first opening 62 in differentialhousing 48. Biasing member 88 may engage head 94 and a portion of firstoutput member 66 at an axially outer end of aperture 78. Biasing member88 may include a compression spring having a spring rate (k) and a freelength (L_(f)) that may be compressed to an installed length (L_(i))when located between head 94 and first opening 62.

First coupling assembly 44 may be adjustable to provide a variablepreload force urging first side gear 68 into engagement with thrustwasher 54 and, therefore, differential housing 48. The preload force maybe adjusted by varying the installed length (L_(i)) of biasing member88. The installed length (L_(i)) of biasing member 88 may be adjustedthrough axial translation of bolt 90 in a direction generally parallelto axis 51. Bolt 90 may be translated axially through rotation thereof,maintaining a threaded engagement with nut 92 and changing the installedlength (L_(i)) of biasing member 88. Head 94 may therefore generallyform a preload adjustment member, as it may be rotated to axiallytranslate bolt 90.

Head 94 may be located outside of differential housing 48 and may berotated in first and second rotational directions generally opposite oneanother. Rotation of bolt 90 in the first rotational direction maygenerally increase a frictional engagement between first output assembly36 and differential housing 48. Rotation of bolt 90 in the secondrotational direction may generally decrease a frictional engagementbetween first output assembly 36 and differential housing 48.

For example, in a first configuration biasing member 88 may have aninstalled length of (L_(i1)) and in a second configuration biasingmember 88 may have an installed length of (L_(i2)). The preload forceurging first side gear 68 into frictional engagement with differentialhousing 48 may generally be defined as F₁=(k)(L_(f)−L_(i1)) for thefirst configuration and F₂=(k)(L_(f)−L_(i2)) for the secondconfiguration. Assuming that L_(i2) is less than L_(i1), F₂ is greaterthan F₁. As such, the first configuration may provide a lesserresistance to relative rotation between first output assembly 36 anddifferential housing 48 due to a lesser frictional engagement betweenfirst output assembly 36 and differential housing 48 resulting from F₁being less than F₂.

First and second coupling assemblies 44, 46 may generally be independentof one another. Therefore, first and second coupling assemblies 44, 46may be adjusted independently of one another. This design flexibilityallows for final assembly preload settings to be adjusted to account formanufacturing variances that may affect the torque required to turn theside gear. In one contemplated method of adjustment after assembly,pinion shaft 22 is rotated while one of the side gears 68 is restrictedfrom rotation. At this time, the one of first coupling assembly 44 andsecond coupling assembly 46 that corresponds to the unrestricted sidegear is adjusted until a desired torque to turn pinion shaft 22 isobtained. The procedure is repeated by restricting the other side gearand adjusting the preload via the other of first coupling assembly 44and second coupling assembly 46 until a desired pinion shaft torque isobtained. Additionally, it should be noted that first and secondcoupling assemblies 44, 46 may be adjusted at locations external todifferential carrier 24 and differential housing 48. As such,disassembly of the differential is not required to set a desired preloador pinion shaft torque.

It should also be appreciated that while two coupling assemblies areshown and described, it is contemplated that a limited slip differentialassembly according to the present disclosure may include only onecoupling assembly. Furthermore, load producing devices other than thecompression springs depicted in the figures may be implemented. Forexample, Belleville washers, torsion springs or elastomeric structuresmay be implemented.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present disclosure can beimplemented in a variety of forms. Therefore, while this disclosure hasbeen described in connection with particular examples thereof, the truescope of the disclosure should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the drawings, the specification and the following claims.

1. A vehicle differential assembly, comprising: a differential housingrotatable about an axis; a first output assembly including a first sidegear and a first output member, said first side gear disposed withinsaid differential housing and being rotatable about said axis, saidfirst output member coupled to said first side gear for rotationtherewith; a second output assembly including a second side gear and asecond output member, said second side gear being disposed within saiddifferential housing and rotatable about said axis, said second outputmember coupled to said second side gear for rotation therewith; a piniongear disposed within said differential housing and engaged with saidfirst and second side gears; and a first coupling assembly engaged withsaid first output assembly and including a coupling mechanism and abiasing member, said coupling mechanism extending through an opening insaid first output member and being displaceable relative to saiddifferential housing in a direction generally parallel to said axis,said biasing member engaged with said coupling mechanism and urging saidfirst output assembly into frictional engagement with said differentialhousing.
 2. The vehicle differential assembly of claim 1 wherein saidcoupling mechanism is displaceable between first and second axialpositions to provide first and second preloads on said first outputassembly to provide said frictional engagement between said first outputassembly and said differential housing, said first preload providing agreater frictional engagement than said second preload.
 3. The vehicledifferential assembly of claim 1 wherein said biasing member urges saidcoupling mechanism in a direction generally parallel to said axis andaxially outwardly relative to said differential housing.
 4. The vehicledifferential assembly of claim 1 wherein said coupling mechanismincludes a bolt and a nut, said bolt including a head and a distal endincluding a thread, said head extending axially outwardly from a firstend of said opening in said first output member and said nut beingdisposed within said differential housing at a second end of saidopening therein, said nut being threadingly engaged with said distal endof said bolt and urging said first side gear into said frictionalengagement with said differential housing.
 5. The vehicle differentialassembly of claim 4 wherein said biasing member is disposed axiallybetween said head of said bolt and said first end of said opening insaid first output member.
 6. The vehicle differential assembly of claim4 wherein said bolt is axially displaceable relative to said firstoutput member.
 7. The vehicle differential assembly of claim 1 furthercomprising a second coupling assembly engaged with said second outputassembly and including an additional coupling mechanism and anadditional biasing member, said additional coupling mechanism extendingthrough an opening in said second output member and being displaceablerelative to said differential housing in a direction generally parallelto said axis, said additional biasing member engaged with saidadditional coupling mechanism and urging said second output assemblyinto a frictional engagement with said differential housing.
 8. Thevehicle differential assembly of claim 7 wherein said first couplingassembly is adjustable to provide said frictional engagement betweensaid first output assembly and said differential housing and said secondcoupling assembly is adjustable to provide said frictional engagementbetween said second output assembly and said differential housingindependently of said first coupling assembly.
 9. The vehicledifferential assembly of claim 1 wherein said coupling mechanismincludes a preload adjustment member disposed outside of saiddifferential housing.
 10. The vehicle differential assembly of claim 9wherein said preload adjustment member is rotatable in a first directionto increase said frictional engagement between said first outputassembly and said differential housing.
 11. The vehicle differentialassembly of claim 10 wherein said preload adjustment member is rotatablein a second direction opposite said first direction to reduce saidfrictional engagement between said first output assembly and saiddifferential housing.
 12. The vehicle differential assembly of claim 1wherein said coupling mechanism extends longitudinally along said axis.13. The vehicle differential assembly of claim 1 wherein said first sidegear is frictionally engaged with said differential housing.
 14. Avehicle differential assembly, comprising: a differential housingrotatable about an axis; a first output assembly including a first sidegear and a first output member, said first side gear disposed withinsaid differential housing and being rotatable about said axis, saidfirst output member coupled to said first side gear for rotationtherewith; a second output assembly including a second side gear and asecond output member, said second side gear disposed within saiddifferential housing and being rotatable about said axis, said secondoutput member coupled to said second side gear for rotation therewith; apinion gear disposed within said differential housing and engaged withsaid first and second side gears; and a first coupling assembly engagedwith said first output assembly and including a coupling mechanism and abiasing member, said biasing member biasing said first output assemblyinto frictional engagement with said differential housing, said couplingmechanism including an adjustment member to vary a load applied by saidbiasing member.
 15. The vehicle differential assembly of claim 14wherein said adjustment member is disposed outside of said differentialhousing.
 16. The vehicle differential assembly of claim 14 wherein saidadjustment member is displaceable to provide a first installed lengthfor said biasing member providing a first preload and a second installedlength of said biasing member providing a second preload that is lessthan said first preload.
 17. The vehicle differential assembly of claim16 wherein said adjustment member is rotatable in a first rotationaldirection to provide said first installed length.
 18. The vehicledifferential assembly of claim 17 wherein said adjustment member isrotatable in a second rotational direction to provide said secondinstalled length.
 19. The vehicle differential assembly of claim 14wherein said adjustment member includes a bolt having a head at a firstend.
 20. The vehicle differential assembly of claim 19 wherein saidcoupling mechanism includes a nut threadingly engaged with a second endof said bolt generally opposite said first end, said nut abutting saidfirst side gear and urging said first side gear into said frictionalengagement with said differential housing.
 21. A method of adjustingpreload within a differential assembly, comprising: restricting rotationof one of a pair of side gears rotatably positioned within adifferential housing; determining a torque required to rotate a pinionshaft drivingly engaged with a ring gear fixed to the differentialhousing; and adjusting the resistance to rotation of the other side gearfrom a position outside of the differential housing to obtain a desiredpinion shaft torque.
 22. The method of claim 21 wherein adjusting theresistance to rotation includes rotating a threaded member to vary aforce output from a biasing member applying a load to the other sidegear.
 23. The method of claim 22 wherein the threaded member extendsthrough the other side gear to a location outside of the differentialhousing.